Maybe because there seems to be a distinct lack of developers interested in creating their A list games for it.
I find most of the 3rd party PR video releases to be a bit sad because it usually looks like they're attempting to show enthusiasm and hype something that they know full well just isn't supposed to be an industry significant release.
I don't think any dev team for a third party company would be particularly thrilled to be working on a Wii title the way things currently are, where success will simply be measured in terms of being able to crank out a title using limited resources that sells well enough to make a profit.